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Joints and Their Classification • Arthrology = study of the joints • Kinesiology = study of musculoskeletal movement • Classified how adjacent bones are joined • Fibrous – by fibrous connective tissue with no space between • Cartilaginous – by pad or bridge of cartilage • Synovial – bones separated by fluid- filled cavity covered by connective tissue • Classified by freedom of movement • Synarthrosis (little or no movement) – fibrous or cartilaginous • Amphiarthrosis (slightly movable) – fibrous or cartilaginous • Diarthrosis (freely movable) – always synovial 7-1 Synarthroses - immobile joints 1. Synostosis - Bony Joint • Gap between two bones ossifies • frontal and mandibular bones in infants • cranial sutures in elderly • attachment of first rib and sternum • Can occur in either fibrous or cartilaginous joint 7-2 Synarthroses -Fibrous Joints • Collagen fibers span the space between bones 1. Sutures - bind skull bones together • Serrate - interlocking lines • coronal, sagittal and lambdoid sutures • Lap - overlapping beveled edges • temporal and parietal bones • Plane - straight, non-overlapping edges • palatine processes of the maxillae 2. Gomphosis • Attachment of a tooth to its socket • Held in place by fibrous periodontal ligament • collagen fibers attach tooth to jawbone • Some movement while chewing 7-3 Synarthroses -Cartilaginous Joint • Synchondrosis • Bones are joined by hyaline cartilage • rib attachment to sternum • epiphyseal plate in children binds epiphysis and diaphysis 7-4 Amphiarthroses - fibrous joint • Syndesmosis • Two bones bound by ligament only • interosseus membrane • Most movable of fibrous joints • Interosseus membranes unite radius to ulna and tibia to fibula 7-5 Amphiarthroses - cartilaginous joint • Symphysis • 2 bones joined by fibrocartilage • pubic symphysis and intervertebral discs • Only slight amount of movement is possible 7-6 Diarthrosis - Synovial Joint Joint in which two bones are separated by a space called a joint cavity Most are freely movable 7-7 General Anatomy • Articular cartilage = hyaline cartilage covering the joint surfaces • Synovial cavity • Articular capsule encloses joint cavity • continuous with periosteum • lined by synovial membrane • Synovial fluid = slippery fluid; feeds cartilages • Articular discs and menisci • jaw, wrist, sternoclavicular and knee joints • absorbs shock, guides bone movements and distributes forces • Tendon attaches muscle to bone • Ligament attaches bone to bone 7-8 Tendon Sheaths and Bursae • Bursa = saclike extension of joint capsule • between nearby structures so slide more easily past each other • Synovial tendon sheaths = cylinders of connective tissue lined with synovial membrane and wrapped around a tendon 7-9 Range of Motion • Degrees through which a joint can move • • • • Nonaxial – vertebrocostal, sacroiliac Monoaxial – elbow, knee,ankle, interphalangeal Biaxial – radiocarpal Triaxial (multiaxial) – sholder, hip • Determined by • structure of the articular surfaces • strength and tautness of ligaments, tendons and capsule • stretching of ligaments increases range of motion • double-jointed people have long or slack ligaments • action of the muscles and tendons • nervous system monitors joint position and muscle tone 7-10 Types of Synovial Joints 7-11
